Process for refining carbonaceous fuels

ABSTRACT

HYDROGEN THE UNDISSOLVED PORTION OF THE TREATED CARBONACEOUS MATERIAL IS MORE READILY SEPARATED FROM THE SOLUTION CONTAINING THE UPGRADED CARBONACEOUS FUEL. IN ADDITION, WHEN SUBBITUMINOUS COAL OR LIGNITE IS TREATED BY THE METHOD OF THIS INVENTION, THE CONVERSION THEREOF AND THE YIELD OF UPGRADED CARBONACEOUS FUEL AS WELL AS THE YIELD OF THE LIQUID BY-PRODUCTS IS SIGNIFICANTLY INCREASED. MOREOVER, WHEN A GASEOUS MIXTURE COMPRISING CARBON MONOXIDE, STEAM AND HYDROGEN IS EMPLOYED, AN UPGRADED FUEL HAVING A LOWER ASH CONTENT IS, GENERALLY, OBTAINED. AN IMPROVED PROCESS FOR PREPARING A LOW-ASH, LOWOXYGEN, LOW-SULFUR CARBONACEOUS FUEL WHEREIN AT LEAST A PORTION OF THE AVAILABLE FUEL FRACTION OF A CARBONACEOUS MATERIAL CONTAINING ASH, OXYGEN AND/OR SULFUR IS DISSOLVEC D IN A SUITABLE AROMATIC SOLVENT IN THE PRESENCE OF A GASEOUS MIXTURE COMPRISING EITHER CARBON MONOXIDE AND STEAM OR CARBON MONOXIDE, STEAM AND HYDROGEN. IT IS ESSENTIAL TO THE PRESENT INVENTION THAT THE SOLVATION BE EFFECTED WITHIN A RELATIVELY NARROW RANGE OF TEMPERATURES AND PRESSURES AND THAT THE PERIOD OF TIME AT WHICH THE CARBONACEOUS MATERIAL IS IN CONTACT WITH THE SOLVENT AT ELEVATED TEMPERATURES AND PRESSURES BE LIMITED WITHIN A RELATIVELY NARROW RANGE. IN A PREFERRED EMBODIMENT, THE CARBONACEOUS MATERIAL TO BE TREATED BY THE METHOD OF THIS INVENTION WILL BE GROUND AND SLURRIED WITH THE SOLVENT PRIOR TO TREATMENT. MOREOVER, IT IS PREFERRED THAT THE AROMATIC SOLVENT EMPLOYED TO BE DERIVED FROM A CARBONACEOUS MATERIAL HAVING THE SAME OR SUBSTANTIALLY THE SAME COMPOSITION AS THAT BEING TREATED. PRODUCTION OF A LOW-ASH, LOWOXYGEN, LOW-SULFUR CARBONACEOUS FUEL BY THE METHOD OF THE PRESENT INVENTION RESULTS IN HIGHER YIELDS OF THE MORE VALUABLE PRODUCTS AND IN PRODUCTS HAVING HIGHER HYDROGEN CONTENTS THAN WHEN HYDROGEN ALONE IS PRESENT DURING THE SOLVATION STEP. MOREOVER, BY USING A MIXTURE OF CARBON MONOXIDE AND STEAM OR CARBON MONOXIDE, STEAM AND

April 30, 1974 w. c. BULL ETAL 3,808,119

PROCESS FOR REFINING CARBONACEOUS FUELS Filed Oct. 12, 1972 UnitedStates Patent 3,808,119 PROCESS FOR REFINING CARBONACEOUS FUELS WillardC. Bull and Bruce K. Schmid, Prairie Village, Kans., assignors to ThePittsburgh and Midway Coal Mining Co., Merriam, Kans., and the UnitedStates of America as represented by the Secretary of the Interior,

a fractional part interest to each Filed Oct. 12, 1972, Ser. No. 297,093Int. Cl. Cg 1/04 U.S. Cl. 2088 11 Claims ABSTRACT OF THE DISCLOSURE Animproved process for preparing a low-ash, lowoxygen, low-sulfurcarbonaceous fuel wherein at least a portion of the available fuelfraction of a carbonaceous material containing ash, oxygen and/0r sulfuris dissolved in a suitable aromatic solvent in the presence of a gaseousmixture comprising either carbon monoxide and steam or carbon monoxide,steam and hydrogen. It is essential to the present invention that thesolvation be effected within a relatively narrow range of temperaturesand pressures and that the period of time at which the carbonaceousmaterial is in contact with the solvent at elevated temperatures andpressures be limited within a relatively narrow range. In a preferredembodiment, the carbonaceous material to be treated by the method ofthis invention will be ground and slurried with the solvent prior totreatment. Moreover, it is preferred that the aromatic solvent employedbe derived from a carbonaceous material having the same or substantiallythe same composition as that being treated. Production of a low-ash,lowoxygen, low-sulfur carbonaceous fuel by the method of the presentinvention results in higher yields of the more valuable products and inproducts having higher hydrogen contents than when hydrogen alone ispresent during the solvation step. Moreover, by using a mixture ofcarbon monoxide and steam or carbon monoxide, steam and hydrogen theundissolved portion of the treated carbonaceous material is more readilyseparated from the solution containing the upgraded carbonaceous fuel.In addition, when subbituminous coal or lignite is treated by the methodof this invention, the conversion thereof and the yield of upgradedcarbonaceous fuel as well as the yield of the liquid by-product issignificantly increased. Moreover, when a gaseous mixture comprisingcarbon monoxide, steam and hydrogen is employed, an upgraded fuel havinga lower ash content is, generally, obtained.

BACKGROUND This invention relates to an improved method for refiningcarbonaceous fuels. More particularly, this invention relates to animproved solvation process for refining carbonaceous fuels.

This invention results from work done under Contract l4010001496 withthe Oflice of Coal Research in the Department of the Interior enteredinto pursuant to the Coal Research Act, 30 U.S.C. 6612668.

It is, of course, well known in the prior art to refine solid,carbonaceous fuels, such as coals, lignites, peat and the like, bydissolving at least a portion thereof in a suitable solvent at elevatedtemperatures and pressures and in a hydrogen atmosphere. Generally,however, the use of these processes has been limited to the preparationof highly specialized products such as waxes and other low volume, highpriced materials due principally to the economics associated therewithas well as other operating difliculties, and few have been concernedwith the production of a low-ash, low-oxygen, low-sulfur carbonaceousfuel in combination with other liquid and gas products. One such processis, however, disclosed and claimed "ice in U.S. Pat. No. 3,341,447 whichissued Sept. 12, 1967 to Willard C. Bull, Lawrence G. Stevenson, Dean L.Kloepper and Thomas F. Rogers and which is assigned jointly to theUnited States of America and Gulf Oil Corporation.

In accordance with the disclosure of this patent, a lowash, low-oxygen,low-sulfur carbonaceous fuel is obtained in combination with both liquidand gas by-products by dissolving a substantial portion of the availablefraction of a naturally occurring carbonaceous fuel in a suitablesolvent. Generally, the solvent will be derived from the original fuelfeed stock. In accordance with the disclosure, it is essential that thesolution be formed under critically controlled conditions oftemperature, pressure and atmosphere and that the same be formed withina relatively narrow, critical range of holding times. Generally, thisprocess has proven quite successful from the standpoint of botheconomics and performance. Notwithstanding this, however, difliculty hasbeen encountered in separating the ash residue from the solution.Moreover, the hydrogen content of the liquid product from this processis generally low and it is sometimes necessary or desirable to furtherhydrogenate this product so as to enhance both its usefulness and value.In addition, the relatively high yields of gas product when compared tothe yield of liquid product detract from the economic attractiveness ofthe process. In addition, the total yield of useful product, which is,generally, economically acceptable with all feed stocks, is undesirablylow with certain feed stocks such as the lignites and subbituminouscoals. As will be readily apparent, it would be most desirable torecover a low-ash, low-oxygen, low-sulfur carbonaceous fuel in thehighest possible yields from any feed stock and to recover by-productstherewith having the maximum possible utility and value. It would alsobe most desirable to obtain these materials with a process having aminimum of operating difficulties.

SUMMARY OF THE INVENTION It has now been found that the foregoing andother disadvantages of the prior art processes can be overcome by themethod of the present invention and a lowash, low-oxygen, low-sulfurcarbonaceous fuel recovered from naturally occurring carbonaceousmaterials in relatively high yields and in combination with valuablebyproducts with a minimum of operating difiiculties. It is, therefore,an object of this invention to provide an improved process for refiningcarbonaceous fuels. It is another object of this invention to provide aneconomical process for preparing low-ash, low-oxygen, low-sulfur fuelsfrom naturally occurring carbonaceous fuels. It is still another objectof this invention to provide an improved process for refiningcarbonaceous fuels wherein the ash may be separated more readily. It isyet another object of this invention to provide an improved process forrefining carbonaceous fuels which will yield liquid products having ahigher hydrogen content. It is a still further object of this inventionto provide an improved process for refining carbonaceous fuels whereinthe liquid by-products are obtained, generally, in higher yields. It isyet a further object of this invention to provide an improved processfor refining carbonaceous fuels wherein the total yield of product fromcarbonaceous materials such as the lignites and subbituminous coals issignificantly increased. Still other objects and advantages of thepresent invention will become apparent from the disclosure set forthhereinafter.

In accordance with the present invention, the foregoing and otherobjects and advantages are accomplished by dissolving all or asubstantial portion of the potentially available fuel fraction of anaturaly occurring carbonaceous fuel in a suitable solvent and in thepresence of both carbon monoxide and steam or carbon monoxide, steam andhydrogen, then separating the undissolved portion of the carbonaceousfuel from the solution, and thereafter recovering a low-ash, low-oxygen,low-sulfur solid, carbonaceous fuel from the solvent. The liquid and gasproducts will be obtained by flashing and/ or fractionation of theliquid media from the solvation step. As is pointed out more fully,hereinafter, it is important to control the operating parameters such astemperature, pressure and atmosphere and to affect the solvation withina relatively narrow range of holding times.

BRIEF DESCRIPTION OF THE DRAWING The figure is a schematic flow diagramof a process within the scope of the present invention wherein therefining of a carbonaceous fuel is effected continuously.

DETAILED DESCRIPTION OF THE INVENTION Broadly, and as has been noted,supra, the present invention relates to an improved process for refiningor upgrading naturally occurring carbonaceous fuels. The refining orupgrading is effected by first dissolving so much of the available fuelportion of the carbonaceous material as is consistent with goodoperation in a suitable solvent. As will be pointed out more fullyhereinafter, it is essential that the fuel fraction of the carbonaceousmaterial be dissolved at an elevated temperature and pressure and in thepresence of both carbon monoxide and steam. The refined or upgradedcarbonaceous fuel is then recovered by first separating the ash portion(undissolved portion) of the carbonaceous feed material and thereafterseparating the dissolved fuel fraction from'the solvent and any liquidand gas by-products produced during the dissolving step.

In general, any carbonaceous fuel may be refined or upgraded to alow-ash, low-oxygen, low-sulfur fuel by the method of the presentinvention. The process is, however, most suitable for the upgrading ofnaturally occurring canbonaceous fuels such as bituminous andsubbituminous coals and lignites. Broadly, the carbonaceous material maybe treated by the method of the present invention in essentially anyshape or size. As will be readily apparent, however, the carbonaceousmaterial will be most easily handled and most readily dissolved when thesame is in a relatively small particle size. For these reasons, then, itis, generally, advantageous to grind or otherwise pulverize the coalsuch that 100 percent will pass through a mesh screen (U.S. Standard)and such that at least 50 wt. percent will pass through a 40 mesh screen(U.S. Standard). In a preferred embodiment, the particle size of thecarbonaceous material treated in accordance with the method of thepresent invention will range between about 0.006 and 0.008 inch indiameter.

It should be noted, that while any carbonaceous material may be treatedby the method of the present invention, the advantageous obtained as aresult of processing by the method of the present invention will varywith the particular carbonaceous feed material subjected to treatmentthereby. In this regard, and as will be pointed out more fullyhereinafter, certain advantages are realized by the method of thepresent invention in the treatment of bituminous coal while the sameand/or other advantages will be realized in the treatment ofsubbituminous coal and these and/or still other advantages will berealized in the treatment of lignites.

In general, any of the solvents known in the prior art to be useful forthe purpose of dissolving the available fuel portion of a carbonaceousmaterial may be used in the method of the present invention. Suitablesolvents include the highly hydrogenated aromatic materials, generally,boiling within a range of about 200 to about 900 F. such as anthraceneoil or creosote oil. A particularly preferred solvent, however, is oneobtained by the extraction of the carbonaceous fuel itself. In thisregard, it should be noted that a liqu d y-p' is obtained as a result ofdissolving the carbonaceous feed material and a portion of this liquidmaterial is suitable for use as a solvent therein. Moreover, asufi'icient quantity of such a solvent will be produced during theextraction to satisfy the process needs therefor in either a batch orcontinuous operation. As will be readily apparent, the composition ofthe solvent thus produced will vary with the particular carbonaceousfeed material but that portion of the liquid by-product having aninitial boiling point within the range of about F. to about 700 F. and afinal boiling point within the range of about 700 F. to about 1100 F., adensity of about 1.1 and a carbon to hydrogen ratio in the range ofabout 1.0209 to about 10:03 will be satisfactory for use in the methodof the present invention.

During the solvation step, it is essential that sufiicient solvent beemployed to effectively dissolve the available fuel portion of thecarbonaceous material being treated without forming a high viscosityslurry which would be difficult, if not impossible, to process upondissolution of the dissolved fuel fraction therefrom. It is, therefore,essential that the ratio of hydrocarbon solvent to the carbonaceousmaterial being treated (on a dry basis) be at least 05:1 and ratios ofhydrocarbon solvent to dry carbonaceous material within the range ofabout 0.5:1 to about 5:1 will be operable in the method of the presentinvention. Higher ratios will, of course, also be operable but suchhigher ratios provide no functional advantage in the process of thepresent invention. Moreover, the use of such higher ratios will requireadditional energy or work for the subsequent separation of solvent fromthe upgraded carbonaceous product and for recycling in the system. Lowerratios within the broad range are, therefore, preferred.

In general, the fuel fraction of the carbonaceous material being treatedby the method of the present invention will be dissolved at atemperature sufficiently high to facilitate the solvation but not sohigh as to cause excessive decomposition of the fuel fraction, which issought to be recovered, or the solvent employed in the extraction orsolvation step. Temperatures within the range of about 700 to about 950F. have been found suitable for use in the present invention. In thisregard, it should be noted that the rate of solvation below about 700 F.is too slow to permit reasonable recovery of the available fuelfraction. At temperatures above about 950 F., on the other hand,decomposition of the desired products and the solvent become excessive.As will be readily apparent, from the standpoint of economics, the useof the lower temperatures within this range which are consistent withgood yields is most desirable.

Since the solvation of the available fuel fraction of the carbonaceousmaterial is accomplished at an elevated temperature and in the presenceof hydrocarbon materials having a boiling point below thesetemperatures, it is essential that the extraction or solvation step beaccomplished at an elevated pressure. Moreover, since elevated pressureenhances the solvation of the available fuel fraction of thecarbonaceous material, it is most desirable to effect the solvation atelevated pressures. In general, pressures within the range of about 500to about 5000 p.s.i.g. will be effective. In this regard, it should benoted that at pressures below about 500 p.s.i.g., the yield of deashedcarbonaceous fuel is unreasonably low. Pressures above about 5000p.s.i.g., on the other hand, are operable but provide no functionaladvantage when employed in the method of the present invention. As willbe pointed out more fully, hereinafter, it is essential that at least aportion of this pressure be provided by a gaseous material or materialscapable'of providing hydrogen ions to the products produced by themethod of the present invention.

As has been noted, supra, the essence of the present invention residesin the discovery of unexpected advantages which are realized when partor all of the available fuel fraction of the carbonaceous material isdissolved in an atmosphere containing both carbon monoxide and steam.Generally, these advantages will be realized when carbon monoxide ispresent in an amount ranging between about 1.5 and 40 s.c.f. of CO perpound of dry coal in combination with steam within the range of about0.2 to 1.5 pounds per pound of dry coal. It is not, however, essentialthat carbon monoxide and steam be the only gaseous components present inthe gas phase during the extraction or dissolving step and, in fact, ithas been found beneficial in many cases to also have hydrogen availablein the gas phase. In this regard, and when hydrogen is employed, theratio of hydrogen plus carbon monoxide to dry carbonaceous feed materialwill range between about 1.5 and 40 s.c.f. per pound of saidcarbonaceous material and the ratio of steam and/or water to drycarbonaceous material will range from about 0.2:1 to 1.5 :1 on a weightbasis. Moreover, when hydrogen is employed, the ratio of hydrogen tocarbon monoxide will range between about 0.1:1 to 10.011.

In general, the length of time during which the solvent and carbonaceousfuel will be contacted at the process temperature will vary betweenabout 3 and 180 minutes. The optimum holding time for each carbonaceousmaterial will, however, vary with each such material. In this regard, itshould be noted that, in general, the viscosity of the solu tionobtained during processing of the carbonaceous material will, initially,increase with time, then decrease and then increase again as the holdingtime is extended. As will be readily apparent, separation of theundissolved portion of the carbonaceous material from the solution andthe recovery of the dissolved fuel portion from the solution will bemost readily accomplished when the viscosity of the mixture from thereactor is at a reasonably low value. For this reason, then, it is mostdesirable to continue the solvent-carbonaceous material contacting atprocess temperature until the viscosity first begins to decrease but todiscontinue the contacting before the viscosity again increases to apoint where the mixture from the dissolver would be difiicult toprocess. In this regard, it should be noted that the viscosity of thesolution in the dissolver can be used to provide an accurate guide todetermine the optimum holding time in the extraction or solvation stepand that this may conveniently be accomplished by reference to therelative viscosity of the solution formed in the dissolver. In thisregard, it should be noted that the relative viscosity here referred tois the ratio of the viscosity of the solution in the dissolver to theviscosity of the solvent used therein. It will, of course, beappreciated that this ratio should be established by determining theviscosities of both the solution and the solvent at the same conditionsand different values might be obtained at different temperatures. Forthis reason, then, the term relative viscosity as used herein isrestricted to and defined as the ratio of the viscosity of the solutionat 210 F. and the viscosity of the solvent, also at 210 F., employed inthe system.

As has been noted, supra, during the extraction or solvation step, thereis, initially, an increase in the solution viscosity followed by adecrease therein and then a second increase. There is, then, acorresponding increase in the relative viscosity followed by a decreasetherein and a second increase. Generally, the relative viscosity willrise, initially, to a value well above 20 before the same begins todecrease as the holding time is continued. This value will, of course,depend somewhat upon the particular carbonaceous material being treatedand the solvent employed in the solvation step. In all cases, however, avalue of at least 20 will be reached during the initial increase.Following this increase, the relative viscosity will reduce to a valuebelow 10, and, generally, to a value well below 5 before the same againbegins to increase. In this regard, it should be noted that mixturesfrom the dissolver having relative viscosities less than 10 can beprocessed by the method of the present invention and a low-ash,low-oxygen, lowsulfur carbonaceous fuel recovered therefrom. Theextraction or solvation will, therefore, be continued at least until therelative viscosity of the solution from the dissolver is less than 10but the same will be discontinued before the relative viscosity haspassed through its minimum and then increased to a value of 10 or more.In a preferred embodiment, the extraction or solvation step will becontinued until the relative viscosity of the solution in the dissolverhas reached a value of 5 or less but will be discontinued before therelative viscosity has increased back to a corresponding value of 5. Ina most preferred embodiment, the extraction or solvation step will bediscontinued when the relative viscosity has reached a value of about1.5 to 2.

While applicants do not wish to be bound by any particular theory, it isbelieved that the solvation of the available fuel portion of thecarbonaceous material being treated is effected via a depolymerizationof the relatively high molecular weight components thereof, "and thatwhen this depolymerization in accomplished in the presence of a hydrogenion donor the free radicals thus formed are neutralized by the hydrogenions, thereby preventing repolymerization of the free radicals. Theneutralized free radicals, as well as any other decomposition products,are then soluble in the solvent and may be subsequently recovered byflashing or otherwise separating the solvent therefrom.

During the extraction or solvation step, materials other than thosewhich are soluble in the solvent are either formed or liberated. Suchmaterials include hydrogen sulfide, carbon dioxide, methane, propane,butane, and other higher hydrocarbons and these materials will comprisepart of the atmosphere in the dissolver. Generally, however, theirpresence therein will not adversely affect the extraction or solvationof the carbonaceous material. Care should, however, be exercised so asto prevent a buildup of these materials to the extent that the partialpressures of carbon monoxide and steam (and hydrogen, when used) arereduced to inoperable values. In this regard, it should be noted thatthese materials may be separated from any recycled gas by conventionalmeans. Moreover, during the extraction or solvation, step, hydrogen isconsumed by the extracted or dissolved portion of the carbonaceousmaterial in an amount rang ing between about 0.5 and 4.0 wt. percent ofthe initial dry coal feed and this amount should be made up if the gasphase is recycled and the presence of hydrogen desired initially. Inaddition, about 5 to about 50 mol percent of the carbon monoxide andsteam will be converted to hydrogen during the extraction or solvationstep and this amount, too, should be made up if gas recycle is employed.

After the extraction or solvation step of the method of this inventionhas been completed, the upgraded, low-ash, low-oxygen, low-sulfurcarbonaceous fuel can then be recovered from solution. Generally, thisrecovery will involve: the separation of the undissolved portion of thecarbonaceous feed material from the solution; the separation of thecarbon monoxide, steam and hydrogen, as well as any other gaseouscomponents present in the system, from the solution; the separation ofthe low-ash, low-oxygen, low-sulfur carbonaceous fuel from the solvent;and the separation of any gas and liquid by-products from the solvent.The manner and order of these separations is not, however, critical tothe present invention and the same may be accomplished in essentiallyany order which will yield the upgraded fuel free of the undissolvedportion of the carbonaceous feed. Generally, however, it will beadvantageous to first reduce the pressure to a value suitable forseparation of the undissolved portion of the carbonaceous feed from thesolution and thereafter separating the gaseous components from theliquid and solid components and then the solid (undissolved portion ofthe carbonaceous feed material) components from the liquid. Theupgraded, low-ash, low-oxygen, low-sulfur carbonaceous fuel can then beconveniently recovered from solution. Fractionation of the solvent phasemay then be employed to effect recovery of the liquid by-product and toseparate any dissolved or entrained gases therefrom.

In general, any suitable means, such as filtration and centrifugation,can be employed to effect the separation of the undissolved portion ofthe carbonaceous feed from the solution. With either of these methods,however, it will, generally, be desirable to subject the recoveredsolids to a drying step so as to recover entrained solvent therefrom.Moreover, the dried solids from a centrifugal separation and/or thedried filter cake from a filter will have a definite fuel value withfuel ratings running as high as 7000 B.t.u./lb.

As will be readily apparent, the gaseous components may be separatedfrom the slurry containing the undissolved portion of the carbonaceousfeed material either prior to or simultaneously with the separation ofthe solid material. After separation, the gases may then be subjected toany subsequent treatment, such as scrubbing to remove acid gascomponents, and then recycled or used for other purposes, as desired. Inthis regard, it should be noted that when gas recycle is employed, abuildup in hydrogen gas will, often, occur, initially, due to theformation thereof through the reaction of carbon monoxide with steam.This inital buildup is not, however, detrimental and, at steady-stateoperation, within the operating ranges heretofore set forth, theconcentration of carbon monoxide and steam in the dissolver can easilybe maintained within the operable limits set forth, supra.

After the undissolved portion of the carbonaceous feed has beenseparated from the solution, the low-ash, lowoxygen, low-sulfurcarbonaceous fuel may then be recovered therefrom with any suitablemeans such as by vacuum distillation or flash evaporation. In any case,however, the solvent and other lower boiling liquids therein will beseparated by exposure to temperatures just slightly above the boilingpoint of the highest boiling component thereof.

The upgraded, low-ash, low-oxygen, low-sulfur carbonaceous fuel may berecovered as either a liquid or a solid, depending upon the particularmethod used to separate the same from the solvent, and the same may beused in either form. Moreover, when the upgraded fuel is recovered as aliquid, the same may be solidified simply by cooling.

As has been noted, supra, the method of the present invention offersseveral advantages over prior art processes wherein hydrogen alone isused to supply the hydrogen required during the extraction or solvationstep. The advantages oifered do, however, vary with the particularcarbonaceous material subjected to treatment. For example, whenbituminous coal is upgraded by the method of the present invention, theyield of all products (gas, liquid and upgraded fuel) from the feed is,often, substantially identical to that obtained through the use ofhydrogen alone. Separation of the undissolved portion of thecarbonaceous feed material from the solution is, however, significantlyenhanced, and as a result, smaller filtration equipment is required toeffect the desired separation. Moreover, when bituminous coal is treatedby the method of this invention, the yield of the more valuable liquidby-product is, generally, increased with a corresponding decrease in theless valuable gas by-product and the hydrogen content of all productsis, surprisingly, higher. When subbituminous coal, on the other hand, istreated by the method of this invention, the advantages noted above andassociated with the treatment of bituminous coal are again generallyrealized. In addition, the total yield of the more valuable products issignificantly increased over the full range of operating conditionsnormally employed. Similarly, when lignite is treated by the method ofthis invention, all of the advantages derived in the treatment ofsubbituminous ooal are, generally, realized and an upgraded fuelcontaining less sulfur is, generally, obtained.

In addition to the foregoing advantages, which advantages will berealized when the solvation is accomplished in an atmosphere comprisingcarbon monoxide and water and any reaction products therefrom eitherwith or without hydrogen being added in the range of concentrationheretofore specified, it has, surprisingly, been found that the additionof hydrogen within the range of concentrations heretofore specified,will, generally, yield an upgraded fuel having a lower ash content thanthat obtained through the use of hydrogen alone. Moreover, sincemixtures of hydrogen and carbon monoxide are, generally, less costlythan either pure hydrogen or pure carbon monoxide, there is a distincteconomic advantage associated with the use of the three componentmixture. In addition, since the presence of steam during the solvationstep is essential to the present invention, there would be no advantagein drying the carbonaceous material prior to subjecting the same totreatment by the method of this invention. In this regard, it should benoted that many carbonaceous materials which may be upgraded by themethod of this invention will contain all of the water required for suchtreatment, and when these materials are treated it will be unnecessaryto add additional steam and/or water.

Having thus broadly described the present invention, it is believed thatthe same will become readily apparent by reference to the appendeddrawing. Referring then to FIG. 1, there is shown a schematic flowdiagram of one embodiment of the present invention wherein acarbonaceous feed material is upgraded in a continuous process. Asillustrated in the figure, a finely ground carbonaceous feed material isfed to mixer or slurry tank 1 through line 2 where the same is slurriedwith a suitable solvent therefor. As illustrated, the solvent entersthrough line 3. After the carbonaceous material has been slurried, thesame is withdrawn from the slurry tank through line 4 and passed throughpreheater 5 and into dissolver 6 through line 7. In the preheater, theslurry is heated to the desired solvation temperature and then held inthe dissolver until the desired portion of the available fuel fractionof the carbonaceous material has been dissolved therein. As has beennoted, supra, it is essential to the present invention that thesolvation be accomplished in an atmosphere comprising carbon monoxideand steam and it is important that the carbonaceous material be incontact with these components at all times during which the same isexposed to elevated temperatures. For this reason, then, it is importantthat the slurry be mixed with the desired gas prior to passing the samethrough the preheater 5. In the embodiment illustrated, the desired gasfeed is brought in through line 8 and mixed with the slurry in line 4.As has been previously noted, the gas fed to the preheater may be purecarbon monoxide, when there is suflicient water in the coal to providethe required steam or when sulficient water is added thereto, or thesame may be a mixture of carbon monoxide and steam or a mixture ofcarbon monoxide, steam and hydrogen. It will, of course, be appreciatedthat other gaseous components could be present in the gas feed and thiswill, generally, be the case when recycle gas is employed or when impuresources of the gas are used. When the solvation step is completed, thesolution containing any undissolved portion of the carbonaceous feedmaterial is withdrawn from the dissolver through line 9 and passed tofilter 10. As has also been noted, supra, other means of separationcould be employed at this point; however, a conventional rotary drumpressure filter suitably adapted for pressure let down and venting ofgases has proven quite satisfactory. In the embodiment illustrated, theseparation of the gaseous components and the undissolved portion of thecarbonaceous feed material is effected simultaneously in the filter. Asillustrated, the gases pass overhead through line 11 to scrubber 12where any undesired components are separated. The treated gas thenpasses overhead through line 13 and all or a portion of the same may bevented through line 14 or recycled to the preheater through line 8. Anymake-up gases required may then be added through line 15. As will bereadily apparent, the undissolved portion of the carbonaceous feedmaterial is deposited on the filter cake and may be withdrawn from thefilter through line 16. The filter cake may then be processed by anysuitable method for the purpose of recovering absorbed solvent or othermaterials. For example, the same may be passed through a rotary drumdrier 17 and then withdrawn from the process through line 18. Thesolvent or other recovered material may then be recovered through line19 and either recycled to the slurry tank or withdrawn from the processas desired. The solution containing the dissolved fuel fraction of thecarbonaceous feed material, on the other hand, is withdrawn from thefilter through line 20 and passed through a second preheater 21. In thepreheater, the solution is heated to a temperature suitable for vacuumflash separation and is then withdrawn through line 22 and passed tovacuum flash vessel 23. The vacuum flash vessel may, of course, beheated as required. In the vacuum fiash vessel, the solvent and anyother liquid materials will be flashed and will pass overhead throughline 24. The overhead product may then be subjected to distillation indistillation column 25. As will be readily appreciated, any number ofproducts may then be recovered from the distillation column. In theembodiment illustrated, the recovered solvent is withdrawn through line26 and may be recycled to the slurry tank through line 3. The lighterliquid materials will pass overhead through line 28 and may be withdrawnfrom the process through this line. In the embodiment illustrated, theupgraded, low-ash, lowoxygen, low-sulfur product will be withdrawn fromthe vacuum flash vessel as a liquid through line 29. The liquid productmay then be cooled and solidified and withdrawn from the process by anysuitable means such as watercooled conveyor 30.

PREFERRED EMBODIMENT In a preferred embodiment, the method of thepresent invention will be employed to upgrade a carbonaceous materialselected from the group consisting of the lignites, the subbituminouscoals and the bituminous coals and the upgrading will be effectedcontinuously. In the preferred embodiment, the carbonaceous feedmaterial will first be ground such that approximately 80% thereof willpass through a 200 mesh (U.S. Standard) screen and then slurried with asolvent derived from the carbonaceous material and having an initialboiling point within the range of about 400 to about 600 F. and a finalpoint within the range of about 800 to about 1000 F. Preferably, theratio of solvent to dry coal in the feed slurry will range from about1.0:1 to about 25:1. The slurry will then be mixed with a gaseousmixture comprising both hydrogen and carbon monoxide. Preferably, fromabout -00 to about 5000 standard cubic feet of these gases will be addedper barrel of slurry. Steam will also be added to the slurry, whenrequired, such that the ratio of water to dry coal ranges between about0.5:1 to about 1:1. The ratio of hydrogen to carbon monoxide will bewithin the range of about 0.321 to 4:1. The slurry will then be heatedto a solvation temperature within the range of about 775 to about 875 F.and the solvation will be effected at a pressure within the range ofabout 1000 to 2500 p.s.i.g. Preferably, the liquid space velocity in thereaction zone will be within the range of about 0.5 to about 3.0.

p.s.i.g. In this run, 96.6% of the available fuel fraction The followingexamples demonstrate the effectiveness of the present invention but arein no way intended to limit the same.

Example 1 In this example, a Kentucky No. 11 bituminous coal was groundsuch that wt. percent thereof passed through a 100 mesh (U.S. Standard)screen and then slurried with amixture of water and a highly aromaticsolvent. The solvent to dry coal ratio in the slurry was 2 to 1. Theratio of water to dry coal was 0.25 to 1. The slurry was heated in anatmosphere comprising 50 mol percent carbon monoxide and 50 mol percenthydrogen at an initial pressure of 1500 p.s.i.g. and held at theseconditions for 30 minutes (at 425 C., the autogenous produced pressurewas 3800 p.s.i.g.). During the 30 minute residence time, 94.1% of theavailable fuel fraction of the carbonaceous feed material was dissolvedin the highly aromatic solvent or otherwise converted to a lowermolecular weight liquid or gas material. After the 30 minute residencetime, the undissolved portion of the carbonaceous feed material wasseparated from the solution by filtration and the gaseous materialsflashed so as to yield a solution containing an upgraded carbonaceousfuel. The upgraded carbonaceous fuel was then recovered by vacuumdistillation of the solvent and other liquid products. The upgradedcarbonaceous fuel was recovered in a yield of 48.7 wt. percent based oninitial coal feed. A liquid product boiling within the range of 100 and800 F. was obtained in a yield of 25 wt. percent based on initial coalfeed and a gas product consisting of C to C hydrocarbons was recoveredin a yield of 1.4 wt. percent based on the initial coal feed. Thehydrogen to carbon ratio in the upgraded carbonaceous fuel was 0.73:1while that in the liquid product was 0.86: 1. The separation of theundissolved portion of the carbonaceous feed material from the solutionwas accomplished in a laboratory filtration apparatus in 1 hour.

Example 2 The run of Example 1 was repeated except that the groundKentucky No. 11 bituminous coal was heated to a temperature of 425 C. inan atmosphere of pure hydrogen and held for 30 minutes. The initialpressure was 1500 of the carbonaceous feed material was dissolved and anupgraded carbonaceous fuel was obtained in a yield of 48.3 wt. percentbased on the initial coal feed. A liquid product having a boiling rangebetween 100 and 800 F., on the other hand, was obtained in a yield ofonly 18 wt. percent based on initial coal feed while a gas productcontaining C -C hydrocarbons was obtained in a yield of 9 wt. percent.Moreover, the hydrogen to carbon ratio in the upgraded fuel was only0.60:1, while that of the liquid product was 0.82:1. In addition,separation of the undissolved portion of the carbonaceous feed materialfrom the solution took 4 hours for the same volume in the samelaboratory filtration apparatus under identical conditions.

From the foregoing, then, it is readily apparent that when the solvationstep is accomplished in an atmosphere containing steam, carbon monoxideand hydrogen there is a significant increase in the yield of liquidproduct without any decrease in the yield of upgraded carbonaceous fueland that the hydrogen contents of the major products are significantlyhigher. Moreover, it is readily apparent that when the solvation step isaccomplished in an atmosphere of steam, carbon monoxide and hydrogen theundissolved portion of carbonaceous feed material can be separated morereadily by filtration.

Example 3 In this example, a Kentucky No. 9 bituminous coal containing3.58 wt. percent sulfur was ground to a particle size such that 100 wt.percent passed through a 100 mesh (U.S. Standard) screen and thenslurried in a highly aromatic solvent having an initial boiling point of550 F. and a final boiling point of 800 F. The ratio of solvent toavailable fuel fraction in the carbonaceous feed material was 2.4 to 1.The slurry was then processed in a continuous flow unit at a temperatureof 425 C. in an atmosphere containing steam, carbon monoxide andhydrogen at a pressure of 1000 p.s.i.g. The hourly liquid space velocityin the reaction zone (preheater plus dissolver) was 0.8 while the hourlygas space velocity (STP) was 225. The weight ratio of steam to coal inthe available fuel fraction was 0.3 to 1 and the mol ratio of hydrogento carbon monoxide in the atmosphere was 1 to 1. At these conditions,87% of the available fuel fraction of the Kentucky No. 9 coal wasdissolved in the highly aromatic solvent and an upgraded carbonaceousfuel was obtained in a yield of 54.8 wt. percent based on initial coalfeed. The sulfur content of the upgraded fuel was 0.8 wt. percent.

Example 4 The run of Example 3 was repeated except that the sol vationof the available fuel fraction in the carbonaceous feed material wasaccomplished in an atmosphere of pure hydrogen. In this run, 90% of theavailable fuel fraction was dissolved in the aromatic solvent and anupgraded carbonaceous fuel was obtained in a yield of 47.1 wt. percentbased on initial coal feed. The sulfur content of this product was,however, 1.02 wt. percent.

A comparison of Examples 3 and 4 clearly reveals that when the availablefuel fraction of a bituminous coal is dissolved in an atmospherecontaining steam, carbon monoxide and hydrogen the sulfur content of theproduct is significantly less than when hydrogen alone is used. This is,of course, particularly significant in light of recent emphasis on theuse of low-sulfur fuels in power plants and other industrialinstallations.

Example 5 In this example, a Big Horn, Wyoming subbituminous coal wasground to a particle siZe such that 100 wt. per cent passed through a 65mesh (U.S. Standard) screen and then slurried in a mixture of water anda highly aromatic solvent having an initial boiling point of 550 F. anda final boiling point of 800 F. The solvent to dry coal ratio in theslurry was 2 to 1. The water to dry coal weight ratio in the slurry was0.4 to 1. The slurry was then heated to 400 C. in an atmospherecontaining 50 mol percent carbon monoxide and 50 mol percent hydrogenand held for 30 minutes. The initial pressure in the reactor was 1500p.s.i.g. During the 30 minute holding time, 76.9% of the available fuelfraction of the Big Horn, Wyoming subbituminous coal was dissolved inthe solution. After the 30 minute holding time, the undissolved portionwas separated from the solution by filtration. An upgraded carbonaceousfuel was then recovered from the solution by vacuum distillation of thesolvent and other liquid components present therewith. The upgradedcarbonaceous fuel was obtained in a yield of 42 wt. percent based oninitial coal feed. In addition, a liquid product having an initialboiling point of 100 F. and a final boiling point of 800 F. was obtainedin a yield of 11.4 wt. percent.

Example 6 The run of Example 5 was repeated except that the solvationwas accomplished at a temperature of 450 C. in an atmosphere of purehydrogen and the solvation step was allowed to continue for 94 minutes.In this run, only 60% of the available fuel fraction of the Big Horn,Wyoming subbituminous coal dissolved in the solvent and an upgradedcarbonaceous fuel was recovered in a yield of only 34.7 wt. percentbased on initial coal feed. Moreover, the yield of total liquid productwas less than 1 wt. percent based on initial coal feed.

1 2 Example 7 In this example, Elkol, Wyoming subbituminous coal wasground to a particle size such that 100 wt. percent passed through a 65mesh (U.S. Standard) screen and then slurried in a mixture of water anda highly aromatic solvent having an initial boiling point of 550 F. anda final boiling point of 800 F. The solvent to dry coal ratio in theslurry was 2 to 1 on a weight basis. The water to dry coal ratio was 0.4to l on a weight basis. The slurry was then heated to 400 C. in anatmosphere comprising 50 mol percent carbon monoxide and 50 mol percenthydrogen and held at these conditions for 30 minutes. The initialpressure in the dissolver was 1500 p.s.i.g. During the 30 minuteresidence time, 92% of the available fuel fraction of the Elkol, Wyomingsubbituminous coal was dissolved in the solvent. After the 30 minuteresidence time, the undissolved portion of the carbonaceous feedmaterial was separated from the solution by filtration. An upgradedcarbonaceous fuel was then recovered by vacuum distillation of thesolvent and other liquid materials therewith. The upgraded carbonaceousfuel was recovered in a yield of 58 wt. percent based on initial coalfeed. At the same time, a liquid product having an initial boiling pointof 100 F. and a final boiling point of 800 F. was recovered in a yieldof 17.6 wt. percent based on initial coal feed.

Example 8 The run of Example 7 was repeated except that the solvationwas accomplished in an atmosphere of pure hydrogen and at a temperatureof 425 C. In this run, only 73% of the available fuel fraction of thecarbonaceous feed material was dissolved in the highly aromatic solvent.Moreover, the yield of upgraded carbonaceous fuel was only 53 wt.percent based on initial coal feed while that of the liquid product wasless than 1 wt. percent based on initial coal feed.

A comparison of Examples 5, 6, 7 and 8 clearly show that when asubbituminous coal is upgraded by the method of the present invention inan atmosphere comprising steam, carbon monoxide and hydrogen a higherpercentage of the available fuel fraction thereof is recovered and theyield of both upgraded carbonaceous fuel and liquid by-product issignificantly increased.

Example 9 In this example, a Beulah lignite was ground to a particlesize such that 100 wt. percent passed through a 65 mesh (U.S. Standard)screen and then slurried with a mixture of water and a highly aromaticsolvent having an initial boiling point of 550 F. and a final boilingpoint of 800 F. The solvent to dry coal ratio in the slurry was 2 to lon a weight basis, and the water to dry coal ratio was 1 to l on aweight basis. The slurry was then heated to a temperature of 410 C. inan atmosphere of pure carbon monoxide and held at these conditions for10 minutes. The initial pressure in the dissolver was 1000 p.s.i.g.During the 10 minute residence time, over 95% of the available fuelfraction of the Beulah lignite was dissolved in the aromatic solvent.After the 10 minute holding time, the undissolved portion of the lignitefeed was separated from the solution by filtration and an upgradedcarbonaceous fuel then recovered from the solution by vacuumdistillation. A liquid product having an initial boiling point of F. anda final boiling point of 800 F. was obtained in a yield of 24 wt.percent based on initial coal feed and a gas product containing C -Chydrocarbons was obtained in a yield of 1.6 wt. percent. The sulfurcontent of the upgradedcarbonaceous fuel was only 0.13 wt. percent.

Example 10 The run of Example 9 was repeated except that the solvationwas accomplished at a temperature of 425 C.

in an atmosphere of pure hydrogen. In this run, only 85% of theavailable fuel fraction of the Beulah lignite was dissolved in thearomatic solvent. The yield of a liquid by-product having an initialboiling point of 100 F. and a final boiling point of 800 F., on theother hand, was only 4 wt. percent based on initial coal feed yvhile thegas product, containing C -C hydrocarbons, was obtained in a yield of 8wt. percent. The sulfur content of the upgraded carbonaceous fuel was0.37 wt. percent.

Example 11 In this example, a Baukol-Noonan lignite containing 31 wt.percent water was ground to a particle sizesuch that 100 wt. percentthereof passed through a 65 mesh (US. Standard) screen and then slurriedwith a highly aromatic solvent having an initial boiling point of 550 F.and a final boiling point of 800 F. The slurry was then mixed with a gasstream consisting of pure carbon monoxide and heated to a temperature of425 C. for 30 minutes. Sufiicient gas was added to make the initialpressure in the dissolver 1000 p.s.i.g. During the 30 minute holdingtime, more than 90% of the available fuel fraction of the Baukol-Noonanlignite feed was dissolved in the solvent. After the 30 minute holdingtime, the undissolved portion of the carbonaceous feed material wasseparated from the solution by filtration. An upgraded carbonaceous fuelwas then recovered by vacuum distillation to remove the solvent andother liquids associated therewith. The upgraded carbonaceous fuel wasrecovered in a yield of 31.8 wt. percent based on dry coal feed. -At thesame time, a liquid product having an initial boiling point of 100 F.and a final boiling point of 800 F. was obtained in a yield of 32.8 wt.percent based on initial coal feed and a gas product containing C Chydrocarbons was obtained in a 7 wt. percent yield based on feed coal.

Example 12 The run of Example 1 was repeated except that the slurry wasmixed with a gas stream comprising 50 mol percent hydrogen and 50 molpercent carbon monoxide. In this run, again more than 90% of theavailable fuel fraction in the lignite feed was dissolved in the highlyaromatic solvent. Moreover, the yield of upgraded carbonaceous fuel,liquid by-product and gas by-product were substantially identical withthose of the previous run and the hydrogen to carbon ratios were notsignificantly changed. The ash content of the upgraded carbonaceous fuelwas, however, significantly lower; viz., 0.12 wt. percent versus 0.45wt. percent.

Example 13 The run of Example 11 was again repeated except that theslurry was mixed with a gas stream comprising pure hydrogen rather thanpure carbon monoxide. In this run, only 59% of the available fuelfraction of the lignite feed was dissolved in the aromatic solvent andthe yield of all products was significantly reduced and the hydrogencontent thereof was significantly lower. Moreover, the undissolvedportion of the lignite feed was separated from the solution at a muchslower rate. 1

A comparison of Examples 9, 10, 11, 12 and 13 clearly indicate that whenlignite is upgraded by the method of the present invention and in thepresence of either-steam and carbon monoxide or steam, carbon monoxideand hydrogen the conversion of the initial materials is significantlyhigher and the yield of desirable products significantly increased.Moreover, the yield of liquid byproduct is significantly higher when thesolvation is accomplished in the presence of either carbon monoxide andsteam or carbon monoxide, steam and hydrogen than when hydrogen alone isused without any decrease in the yield of upgraded carbonaceous fuel.These examples also demonstrate that the hydrogen content of theproductsis; generally, higher when the gas mixture is employed than whenhydrogen alone is used and that the' sulfur content of the upgradedcarbonaceous fuel is significantly lower. Moreover, it is clear from thecomparative examples that when a mixture of steam, carbon monoxide andhydrogen is employed, the ash content of the upgraded carbonaceous fuelis lower. Further, it is readily apparent from a comparison of theseexamples that when the carbonaceous feed material contains a sufiicientamount of water therein it is unnecessary to add steam during thesolvation step.

Although the present invention has been described and illustrated byreference to particular embodiments thereof, it will be readily apparentthat the same lends itself to various modifications which will beobvious to those of ordinary skill in the art. Accordingly, referenceshould be made solely to the appended claims to determine the scope ofthe invention.

Having thus described and illustrated the present invention, what isclaimed is:

1. A solvation process for preparing a substantially ash-free solidcarbonaceous fuel from a charge consisting essentially of coalcontaining ash, an aromatic solvent, a. gaseous carbonmonoxide-containing stream, with or without a gaseoushydrogen-containing stream and with or without added water, comprisingthe steps of:

(a) dissolving in the aromatic solvent at least a portion of thecarbonaceous fuel fraction from the ash of the coal at a temperaturewithin the range of about 700 F. to about 950 F. and at a pressurebetween about 500 and 5,000 p.s.i. in contact with between about 1.5 and40 standard cubic feet of carbon monoxide per pound of dry coal andbetween about 0.2 and 1.5 pounds of steam per pound of dry coal to forma dissolved solution;

(b) establishing the dissolving conditions so that the relativeviscosity of the solution measured at 210 F. rises to a value at least20 times the viscosity of the solvent alone measured at 210 F. due toextration of carbonaceous fuel from the coal by the solvent and thenfalls to a value below 10 times that of the solvent alone measured at210 F. due to depolymerization of said carbonaceous fuel;

(c) the dissolving conditions permitting the relative viscosity of thesolution to again rise above 10 with increased dissolving time due torepolymerization of said carbonaceous fuel but terminating dissolvingconditions which permit the relative viscosity to again rise above 10;

(d) separating the undissolved portion of the coal from the solution;

(e) recovering an upgraded substantially ash-free carbonaceous fuel fromthe solution; and 1 (f) cooling and solidifying said fuel and removingsolid, substantially ash-free fuel from the process.

2. In the process of claim 1, terminating the dissolving conditions whenthe relative viscosity has fallen from a value above 20 to a value below5, the dissolving conditions permitting the relative viscosity to againrise above 5 except for termination of the dissolving conditions whichpermit said rise.

3. In the process of claim 1, terminating the dissolving conditions whenthe relative viscosity has fallen to a value below 2, therdissolvingconditions permitting the relative viscosity to again rise above 2except for termination of the dissolving conditions which permit saidrise.

4. The process of claim 1 wherein the ratio of solvent to dry coal iswithin the range of about 0.5 to 1 to'about 5 to 1 5. The process ofclaim 4 wherein said solvent has an initial boiling point within therange of about to about 700 F. and a final boiling point within therange from about 700 F. to about 1100 F.

6. The process of claim 4 wherein said solvent is derived from a coalhaving a composition substantially identical to that of the coal beingtreated.

7. The process of claim 1 wherein said coal is first ground and thenslurried in said solvent.

8. The process of claim 1 wherein the carbonaceous fuel fraction of thecoal is dissolved at a temperature within the range of about 775 toabout 875 F.

9. The process of claim 1 wherein the carbonaceous fuel fraction of thecoal is dissolved at a pressure within the range of about 1000 to about2500 p.s.i.g.

10. The process of claim 9 wherein the ratio of solvent to dry coal iswithin the range of about 1.0 to 1 to about 2.5 to 1.

11. The process of claim 1 wherein hydrogen is included in the charge tosaid dissolving step.

References Cited UNITED STATES PATENTS 3,075,912 1/ 1963 Eastman et al.2088 3,692,662 9/1972 Wilson et al. 2088 5 3,733,183 5/1973 Singh 20883,748,254 7/1973 Gorin 208-8 DELBERT E. GANTZ, Primary Examiner 10 V.OKEEFE, Assistant Examiner US. Cl. X.R. 208-l0

